清空已有内容，render默认为首次渲染
清空已有内容，render默认为首次渲染

noikiy/zrender,armslave00/zrender,dasmond/zrender,lkiarest/zrender,uooo/zrender,powy1993/zrender,KnightBubble/zrender,skyujilong/zrender,jl9n/zrender,ecomfe/zrender,ilovezy/zrender,coderstudy/zrender,stanleyxu2005/zrender,ecomfe/zrender,noikiy/zrender,ilovezy/zrender,ekinwei/zrender,songshuang00/zrender,elancom/zrender,dato-code/zrender,dasmond/zrender,jl9n/zrender,elancom/zrender,ecomfe/zrender,IveWong/zrender,laomu1988/zrender,nagyistoce/ecomfe-zrender,uooo/zrender,powy1993/zrender,ekinwei/zrender,dato-code/zrender,armslave00/zrender,nagyistoce/ecomfe-zrender,lkiarest/zrender,ChaosPower/zrender,stanleyxu2005/zrender,KnightBubble/zrender,skyujilong/zrender,IveWong/zrender,laomu1988/zrender,powy1993/zrender,coderstudy/zrender,ChaosPower/zrender,songshuang00/zrender